It is well known in the art that hydrocarbon feedstocks containing varying amounts of metals such as nickel, vanadium and iron cause deterioration of the cracking catalyst during the cracking process. In fact, some oils contain these metals in such a high concentration that they cannot be economically cracked into gasoline and other fuels. The metals accumulate on the cracking catalyst and cause increased hydrogen production and coke laydown on the cracking catalyst, thereby adversely affecting the yield of desired products.
It has heretofore been proposed to passivate these metals by treating the contaminated catalyst with antimony oxide or a compound convertible to antimony oxide. While this process has proven to be very successful, there is required the incurring of additional cost due to installation of additional feeding means to introduce the passivatng agent into the cracking system.